1. Field of the Invention
The present invention relates to a manufacturing method of a semiconductor device, a semiconductor device, and a method of printing on a semiconductor wafer, and, more particularly, to a manufacturing method of a semiconductor device, a semiconductor device, and a method of printing on a semiconductor wafer including technology to form printed letters for semiconductor wafer identification using a laser.
2. Description of the Related Art
In order to restrain a latch up phenomenon while easily achieving insulative separation between neighboring elements, semiconductor devices have traditionally been manufactured using a silicon on insulator (SOI) substrate. The SOI substrate has a structure in which a silicon substrate and a silicon thin film (SOI layer) are separated from each other by an embedded oxide film in an insulative state, i.e., a structure in which materials (silicon) of the same kind are joined to each other via an embedded oxide film, which is a dielectric film.
In recent years, a structure in which an insulative substrate formed of sapphire or quartz is used and different materials are joined to each other has been used in place of a structure having a silicon substrate and an embedded oxide film. In particular, a substrate formed of sapphire is referred to as a silicon on sapphire (SOS) substrate, and a substrate formed of quartz is referred to as a silicon on quartz (SOQ) substrate. Since the sapphire SOS substrate or the quartz substrate exhibits electrical insulation, various semiconductor elements formed at such a substrate may have little parasitic capacitance, excellent high frequency properties, and low power consumption.
Also, in a manufacturing process of a semiconductor device using the SOT substrate, the SOS substrate, or the SOQ substrate, printed letters for wafer identification are formed at a silicon thin film at which a semiconductor element is formed. Such printed letters enable process history, place of production, or properties of a wafer to be easily recognized even during the manufacturing process of the semiconductor device. For example, Japanese Patent Kokai No. 2006-100724 (Patent document 1) discloses a method of irradiating a laser to a silicon thin film of a SOS substrate to form printed letters (that is, to perform laser marking).
Also, since sapphire and quartz substrates transmit visible light, it may be difficult to perform positioning in the direction perpendicular to the surface of a wafer during manufacture of a semiconductor device. In order to solve such a problem, a light reflection film, made of a material, such as silicon nitride, which does not transmit visible light, is formed at the bottom of the sapphire substrate or the quartz substrate (the surface opposite to the surface at which a silicon thin film is formed), which is well-known technology.